In recent years, a mydriatic/non-mydriatic combination type fundus camera has been used in an ocular fundus observation apparatus, particularly in a fundus camera, to reduce a burden of a subject as much as possible. The mydriatic/non-mydriatic combination type fundus camera can perform mydriatic photographing and non-mydriatic photographing corresponding to contents of examination by one fundus camera.
Generally, infrared light is used in observation before non-mydriatic photographing, and visible light is used in observation before mydriatic photographing. In Japanese Patent Application Laid-Open No. 7-100112, it is discussed that visible light and infrared light are selectively used as an observation light source of an eye to be examined and a wavelength of an alignment index projection light source is changed corresponding to the observation light source, thereby improving visibility of an alignment index.
In Japanese Patent Application Laid-Open No. 2003-305009, a fundus camera is discussed which selectively uses visible light and infrared light as a light source of observation of an eye to be examined and uses near infrared light as an alignment light source. This fundus camera improves visibility of an alignment index by increasing a quantity of light of the alignment light source in case of visible light observation more than that in case of infrared light observation.
In Japanese Patent Application Laid-Open No. 2000-287934, a position for projecting an alignment index is shifted in a direction of an optical axis in case of photographing a center of an ocular fundus of an eye to be examined and in case of photographing the periphery thereof, thereby suppressing occurrence of flare.
However, as discussed in Japanese Patent Application Laid-Open No. 7-100112, when a wavelength of an alignment index projection light source is changed, a focus is changed with a difference between the wavelengths and an alignment index is deviated there from. Thus, it becomes difficult to obtain correct focus.
Further, a method discussed in Japanese Patent Application Laid-Open No. 2003-305009 in which an alignment index is provided by near infrared light and the luminance thereof is changed corresponding to an observation wavelength, is needed to enhance the intensity of light of less-visible wavelength in visible light observation. Even if this method can be recognized by an examiner, visibility is hardly excellent for a subject.
A method discussed in Japanese Patent Application Laid-Open No. 2000-287934 in which the position for projecting the alignment index is shifted to suppress occurrence of flare is not devised a measure to improve the visibility when the characteristic of the observation light source is changed.